1. Field of the Invention.
This Invention relates to the side wall and side post construction of open top containers for moving, transporting and storing materials.
2. Summary of the Prior Art
Open top containers for moving or storing materials generally have a bottom, side walls and end walls. The container is basically open at the top but may have a removable cover or have a non-rigid closed top. Examples of such containers are truck trailers, rail cars or scrap gondolas and are illustrated in U.S. Pat. No. Des. 238,259 and U.S. Pat. No. 4,252,067.
The conventional configuration for the side wall of these containers is a bottom rail attached to a horizontal rectangular floor and to vertical side posts and flat sheet material to which is attached a top rail. The cover sheets of material are rigidly fastened to the bottom rail, vertical studs and top rail to form the container. The top and bottom rails are designed to carry the vertical load of the material in the container similar to the top and bottom flanges of a conventional I-Beam and the flat cover sheets serve as, both, the web of a conventional I-Beam and the enclosing wall to contain the load. The side posts of prior art are designed and rigidly placed to support the flat cover sheets in containing the load and to resist the outward horizontal forces while, also, transmitting any forces on the bottom rail directly to the top rail.
In both open top and closed top containers, the bottom rail is in tension and the top rail is in compression. In open top containers, however, the top rail is in non-laterally supported compression and must, therefore, be designed as a column to carry the load within the container. As loads are increased, the compressive force is increased tending to buckle or bow the top rail outwardly requiring an increase in size and/or lateral support with cross ties to prevent buckling failure. Such cross ties are undesirable for freely loading and unloading the container and are subject to damage or removal by the container user. Thus, conventional open top container designs have relied on the top rail to carry the downward forces of the load as a beam and on cross ties or increased size to offset the compressive buckling of the top rail.